This invention relates generally to gas turbine monitoring and testing practices and, more specifically, to a metalized ceramic Kiel-type pressure sensor used to gather total pressure and/or total temperature data from the surrounding flow in the hot gas path of a turbine engine.
Kiel-type pressure sensor probes are often used to measure total pressure in a fluid environment where the direction of flow is not known or changes with operating conditions. Associated pressure tubing connects the probe to a transducer where the pressure measurement is translated to a signal for routing to a data acquisition system. The Kiel-style probe has a shroud to protect the pressure tubing. The shroud makes the probe insensitive to a range of yaw and pitch angles because the flow is straightened as it enters the probe. Kiel-style probes can be installed in a variety of turbine components/locations, for example, in a low-pressure steam-turbine exhaust duct, enabling measurement of the total pressure distribution exiting the last-stage row of buckets during performance testing. U.S. Pat. No. 4,433,584 exemplifies the use of a plurality of Kiel-style probes (referred to hereinafter as “Kiel probes”) on a rake downstream of a turbine section. In addition, Kiel probes are sometimes mounted in the hot gas path of the turbine. i.e., on components of the gas turbine that are contacted by the hot combustion gases, especially in the first and second stages of the gas turbine.
Traditional Kiel probe shrouds or housings used in gas turbine applications, and especially those mounted on nozzles in the hot gas path, have been made from high-temperature alloys. Even these high-temperature alloys, however, cannot withstand the temperature in the first stage and sometimes even in the second stage of modern gas turbines where temperatures can reach 2300° F. Unless active cooling schemes are employed to cool the metal alloy shrouds, the shrouds may well disintegrate under the extremely high temperatures. While platinum is an option for the shroud composition, it is very expensive and thus rarely if ever used in Kiel probe applications.
Ceramic materials, while able to withstand the high temperatures in the hot gas path of the gas turbine, are difficult to bond to the host metal alloy nozzle or other metal alloy turbine component.
There remains a need therefore, for a relatively low-cost Kiel probe shroud construction that will survive the high-temperature environment of a gas turbine hot gas path.